Refrigerating apparatus



May 31, 1932.

F. J. HEIDEMAN 1,861,089

REFRIGERA'II NG APPARATUS Filed Oct, 31,,

Patented May 31, 1932 UNITED STATES PATENT OFFICE FREDERICK J. HEIDEMAN, OF DAYTON, OHIO, ASSIGNOR TO FRIGIDAIRE CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE REFRIGERATING APPARATUS Application filed October 31, 1929.' Serial No. 403.731.

This invention relates to refrigerating apparatus and particularly to apparatus for returning oil from the evaporator to the compressor of a refrigerating system.

6- One of the objects of the invention is to provide means wherebythere is not an excessive amount of oil in the evaporator of a refrigerating system.

Another objectof the invention is to provide means whereby the oil blanket on a liquid refrigerant inthe evaporator is limited to a definite maximum thickness.

. Another object of the invention is to providemeans for allowing the evaporation of any liquid refrigerant absorbed in the oil to evaporate before returning the 'oil from the evaporator to the compressor.

- Further objects and advantages of the present invention will be apparent from the f01-- 29 lowing description, reference being had to the accompanying drawings,-wherem a preferred form of the present invention-is clear ly shown.

' In the drawings:

Fig. 1 is a cross section through an evaporator illustrating an application of the invention;

Fig. 2 is a top view of'one form ofsuction return tube in Fig. 1; A

Fig. 3 is a diagrammatic illustration of a refrigerant system in which the invention has been installed; I

Fig. 4 is an end View of a slightly different suction tube; and

Fig. 5 is a side view of Fig. 4 with aprotective. screen.

One of the problems in connection with refrigeration systems is that of the circulation through the system of thelubricant supplied to the compressor for the necessary lubrication of its moving parts. The vaporized refrigerant is generally drawn to the compressor by suction created by the pump action of the compressor and on being compressed is forced under pressure to the other elements of the refrigerating system. This process'of suction, xcompressing and forwarding by pressure is apt toturn the oil into a foamy state and to carry certain portions or itto other portions of the refrigerating system where it isnot desired. Furthermore as the compressor" generally has the pumping action above referred to, a certain portion of the oil is mechanically carried along with the re frigerant in addition to that absorbed by the refrigerant gas. This oil eventually reaches the evaporator and, where a refrigerant such as sulphur dioxide is used, the oil will form a blanket on the top of the liquid refrigerant in the evaporator.

If too much oil is drawn from the evaporator it may result in the moving parts of the evaporator being damaged for want of sufiicient" lubricant. If the oil blanket be comes very thick on the surface of the liquid refrigerant in the evaporator it decreases the efliciency of the evaporator by taking the I place of the refrigerant and furthermore by hindering the suitable rate of vaporization of liquid refrigerant. Accordingly it is one of the objects of this invention to provide means for. returning any excessive oil in the evaporator promptly to the compressor. It is also desired, however, to prevent any liquid refrigerant from also returning with the oil to the compressor. There is, of course, a decrease of efficiency where the liquid refrigerant is not evaporated within the evaporator. However, the presence of'liquid refrigerant in the return conduitwill cause a frosting of a refrigerant return line and on the off cycle this frost will melt and cause ylery undeslrable puddles of water upon the oor.

It is also desired to accomplish the result above outlined without the use of additional apparatus but by the use of elements hereto-.

fore used in a somewhat modified shape. Not only are means provided for the return of the oil but also the same means limits the oil blanket to a definite maximum thickness.

More specifically the invention contemplates a change in the usual suction line or return tube from its upwardly extending position to a. shape that will curve downwardly toward the surface of the liquid. Furthermore instead ofthe wide open end this end is restricted either into a very narrow vertical slot or a restricted lower end portion that opens into an adjacent portion having a cross sectional area. The position of the narrow end of this vertical slot or restricted lower end portion will determine the height of the oil level. The moment the oil reaches the tip of this restricted portion, the oil would be attracted upward into this tube by capillary attraction to the sides of the restricted portion. The restricted portion has the additional function of increasing the velocity of the gas therethrough with the result that the oil is carried up the tube by refrigerant gas passing through. When the oil reaches the portion having a. larger and broader cross sectional area the gas will decrease its velocity and any liquid refrigerant absorbed therein will be evaporated while still in the tube of the evaporator. The oil will pass out the suction line port with the gas and return to the com ressor.

In Fig. 1 is disc osed a preferred type of evaporator to which the invention has been applied. This evaporator preferably is composed of a tank or boiler 10 generally of brass with closure member or valve plate 11 extending across its open cylindrical end. It is preferable to have a supporting member 13 around the opening of the tank to support the rim and also to receive the fastening screws 12 of the closure member. A plurality of depending ducts or tubes 14 also prefer ably extend along the under portion of the tan An entrance port 15 is located preferably on the lower portion of the valve plate to permit entrance. of the liquid refrigerant 21 to the boiler. A boss 16 preferably surrounds this port on the inner of the valve plate and has attached thereto a bracket 17 supporting a needle valve 18 extending into a restricted opening in the boss. This needle valve 18 is operated by a. float ball 19 on a float ball arm 20. As the liquid refrigerant evaporates and allows the float valve to sink, the needle valve is opened and the evaporated refrigerant is replaced by more liquid refrigerant. Accordingly there is always a substantial constant amount of liquid refrigerant within the tank or boiler.

As previously explained the lubricant is generally carried along with the liquid refrigerant and, of course, when such lubricant reaches the evaporator and where refrigerant like sulphur dioxide is used, this lubricant will form an oil blanket 22 on the surface of the liquid refrigerant. When this oil blanket is very thick the efliciency of the apparatus is decreased due to the displacement of liquid refrigerant and also due to the decrease of evaporation of the liquid refrigerant due to the oil blanket. This decrease of efficiency is noticeable where the oil blanket exceeds a thickness of three-fourths of an inch. Accordingly the invention contemplates modifyingthe usual return tube for the gaseous refrigerant so that this oil blanket will be limited to any desired maximum thickness and might even be practically eliminated.

The return tube 25 for conducting evaporated gas to the outlet port 26 an suction return valve 27 is shaped preferably to curve downwardly towards the surface of the liquid in the tank. The end 30 of the tube in the modification disclosed in Fig. 2 has an elongated narrow slot 31 in a vertical plane. The under part of the'tube has a downwardly sloping surface ending at the point 33. The narrow restricted slot provides entrance to an adjacent portion 34 of the tube having a greater cross sectional area. The end of the tube is also preferably sloping although it may even be vertical. However, it is preferred to have it sloping as disclosed to avoid any carrying of liquid refrigerant into the opening. A plurality of openings 35 are also made in the upper portion of the tube to permit additional entrance of the gas into the portion 34 of larger cross sectional area and cause a decrease in velocity so any liquid refrigerant drawn through the end 30 will be deposited here.

In operation the oil blanket accumulates upon the surface of the refrigerant and will finally reach the tip of the tube and will be drawn up to this narrow restricted tip portion by capillary attraction. The velocity of evaporated gas in the tank will be greater through the narrow restricted slot than it would be if the tube had a wide mouth. Accordingly as the gaspasses through this narrow openingwith increased velocity it will draw the oil up the sloping bottom portion of the tube with it into the larger part of the tube. More oil, of course, will be drawn upwardly all the time as long as the oil is in contact with the tip of the tube. After the gas and oil reaches this portion of the tube having a greater cross sectional area it will allow any liquid refrigerant in the oil and gas to evaporate. The oil and gas will then pass through the suction port and valve. The surface of the liquid refrigerant is definitely fixed and controlled by the float ball operating the needle valve.

If the surface of the liquid refrigerant is known the position of the tip of the tube can be placed to definitely limit the thickness of the oil blanket on top of the liquid refrigerant. If it is desired, for example, to limit the oil blanket to that of one-fourth inch the tip will be placed so that it willcome onefourth of an inch above the surface of the liquid refrigerant as determined by the float ball. If desired, the tip could be placed substantially at the surface of the liquid refrigerant and in this case the oil would be withdrawn from the evaporator practically as soon as it came into the evaporator. ow ever, this close setting of the tip to the surface of the liquid refrigerant might increase the I the possibility of liquid refrigerant being drawn up into the tube.

In Fig. 4 is disclosed another modification in shape of the end of the tube which will be called 36. This tube has the sloping bottom 37 ending in a tip 38 similar to the tip 33. Instead of a narrow slot, the lower end of this tube has a pointed V-shape portion 39. The lower portion of the V is of course gradually restricted and the lubricant or other liquid been installed preferably comprises the usual compressor for withdrawing the evaporated refrigerant from the evaporator by means of a suction action through the suction line or conduit 46. Upon suitable compressing the refrigerant gas, generally by a pumping action, the compressor forwards the compressed refrigerant gas to the condenser 47 where it is liquefied and preferably deposited in the receiver 48. When required, it is forwarded from the receiver by the liquid supply conduit 49 to the evaporator. A motor 50 is connected, such as by the belt means 51 for operating the compressor. It is also preferred to have a temperature pressure responsive means 52 for automatically controlling the operation of the motor in response to conditions in the evaporator. This means is preferably connected in the suction line conduit and is also of the well known bellows type operating a snap switch. The system from the compressor through the condenser, receiver and to the liquid valve of the evaporator valve plate is generally referred to as the high pressure side of the system. The evaporator and its connections to the crank casing of the compressor are generally referred to as the low pressure side of the system. V

The shape of the outlet tube is subject to Variation in addition to the two forms disclosed in Figs. 2 and 4. In general the form disclosed in' Fig. 2 is to be used on smaller installations. The form in Fig. 4 is to be used generally in commercial installations Where it is necessary to return a large volume of gas to the compressor.

The invention is of course not limited to the removal of oil alone, as other liquids not desired in the evaporator could also be removed by the invention.

Accordingly there has been disclosed a very positive means for returning the oil from the evaporator to a compressor and one that definitely limits the maximum thickness of the oil blanket to a predetermined amount. Furthermore this result is accomplished without the addition of any other means unusual in the evaporator but by merely modifying the shape and form of the usual parts of an evaporator.

While the formof embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An evaporator comprising a casing adapted to contain a quantity of liquid refrigerant, .means for maintaining a substantially constant quantity ofsaid liquid refrigerant in said evaporator, a second liquid adapted to be carried to said evaporator with said refrigerant, said casing having an outlet port for the evaporated refrigerant gas, conducting means extending from said outlet towards the surface of said second liquid and having an opening for the vaporized-refrigerant, said opening being formed to provide a restricted area extending to a point adjacent the normal refrigerant level in said evaporator for drawing said second liquid therein by capillary attraction, and a screen at the open end of said conducting means for preventing-splashing of liquid refrigerant therein.

2. An evaporator comprising a casing adapted to contain a quantity of liquid refrigerant, means for maintaining a substantially constant quantity of said liquid refrigerant in said evaporator, a second liquid adapted to be carried to said evaporator with said refrigerant, said casing having an outlet port for the evaporated refrigerant gas, conducting means extending a substan tial distance into the evaporator from said outlet and having an opening for the vaporized refrigerant, said opening being formed to provide a restricted area extending downwardly at an angle to a point adjacent the normal refrigerant level in said evaporator for drawing said second liquid therein by capillary attraction, and a screen at the open end of said conducting means for preventing splashing of liquid refrigerant therein.

3. An evaporator comprising a casing adapted to contain a quantity of liquid refrigerant, means for maintaining a substantially constant quantity of said liquid refrigerant in said evaporator, a second liquid adapted to be carried to said evaporator with said refrigerant, said casing having an outlet port for the evaporated refrigerant gas, conducting means extending from said outlet towards the surface of said second to provide a restricted area extending to a point adjacent the normal refrigerant level in said evaporator for drawing said second liquid therein by capillary attraction.

4. An evaporator comprising a casing adapted to contain a quantity of liquid refrigerant, means for maintaining a substantially constant quantity of said liquid refrigerant in said evaporator, a second liquid adapted to be carried to said evaportor with said refrigerant, said casing having an outlet port for the evaporated refrigerant gas, conducting means extending a substantial distance into the evaporator from said outlet and having an opening for the vaporized refrigerant, said opening being formed to provide a restricted area extending downwardly at an angle to a point adjacent the normal refrigerant level in said evaporator for drawing said second liquid therein by capillary attraction.

5. An evaporator comprising a casing adapted to contain a quantity of liquid refrigerant, means for maintaining a substantially constant quantity of said liquid refrigerant in said evaporator, a second liquid adapted to be carried to said evaporator with said refrigerant, said casing having an outlet port for the evaporated refrigerant gas, conducting means extending a substantial distance into the evaporator from said outlet and having an opening for the vaporized refrigerant, said opening including a restricted portion sloping gradually to a point adjacent the normal refrigerant level in said evaporator for drawing said second liquid therein by capillary attraction.

In testimony whereof I hereto afiix my signature.

FREDERICK J. HEIDEMAN. 

